1. Field of the Invention
The present invention is related to a method for forming a scaffold, particularly to a scaffold-forming method that has a fixation process at low temperature.
2. Description of the Prior Art
Tissue engineering, a technique to create new tissue from cultured cells, has now been considered as a potential alternative to organ or tissue transplantation. A key technique in tissue engineering is to prepare biodegradable scaffolds with suitable structure for cell culture. The functions of scaffolds include:    a. delivering the cells or inchoate tissue to a specific location in the human body, so as to keep the cells or tissue from damages caused by the human immune system or other physical effects of the human body;    b. constructing new tissue or organs into needed three-dimensional structure and providing support and protection;    c. stimulating the cells or tissue to perform specific functions; for example, some requested effects can be achieved by coating specific signal-generating agents on scaffolds.
Conventional methods for forming scaffolds include phase separation and non-phase separation methods. The phase separation method is a method in which pores are formed via phase separation. Common examples are thermally-induced phase separation and nonsolvent-induced phase separation. On the other hand, common non-phase separation scaffold-forming methods include leaching, three-dimensional printing, gas foaming, and sintering of half-melted polymer particles.
Freeze-drying is a widely used scaffold-forming phase separation method. The method comprises two processes: the freezing process and the drying process. First of all, the temperature of the prepared polymer solution is lowered to transfer the solution from homogeneous state to heterogeneous state. While transferring, the solution is separated into two phases which are polymer-rich and polymer-poor phases. The polymer-poor phase then becomes the pores and the polymer-rich phase becomes the pore walls after the solvent is removed. In other words, the porous structure takes shape when the polymer solution is frozen. To obtain porous scaffolds, the porous structure resulted from freezing should be carefully retained during the stage of solvent removal. The reason why freeze-drying is widely used is that the solvent is vacuum-dried at a temperature low enough to prevent damage to the porous structure. Nonetheless, the freeze-drying method comes with some limitations as follows:    a. limited solvent options: to be utilized in the freeze-drying method, often a highly volatile solvent is preferred so as to avoid difficulties in solvent removal caused by the low vapor pressure at low drying temperature;    b. considerable power consumption: the freezing equipment requires huge power consumption, which is often an obstacle to large-scale production;    c. a time-consuming process: a long period of time is required to completely remove the solvent because of the inherent low volatility of solvent at low temperature; for example, a couple of days won't guarantee complete removal when a solvent with a high boiling point comes into consideration,
Therefore, a new method for forming scaffolds is still needed corresponding to both economic effect and utilization in industry.